Archive for the ‘Do It Yourself’ Category:

2020-11-02 Signal Tracer Or Audio Amp From An Old AM Radio

Its not hard to make a signal tracer from an old AM radio. You need 60 mm of red and black flexible twisted pair, a 0.22 uF, 100V capacitor, a small black alligator clip, a 50 mm length of shrink tubing that will fit over the following probe, and a thin 100 mm long piece

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2020-10-11 Right To Repair

This morning on CBS Sunday Morning they had an article about a farmer who couldn’t repair his $800,000 John Deere tractor and lost several days of work. There is a growing movement in the US to make laws that require manufacturers to allow their customers to repair the equipment they own. This is a backlash

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2020-07-11 DIY Off Grid Solar System

This is a YouTube video. This guy did a very good job of building an off-grid solar system. It’s transportable, uses four 100 watt panels, two 12V AGM batteries in parallel, can supply 120VAC pure sine wave at 2000 watts and costs under $1,900. This is an excellent video with plenty of details. He calls

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2020-07-11 Lawn Sprinkler System Losing Pressure?

I’ve been seeing the sprinklers reaching a smaller radius after several years, and brown spots between. I was thinking that it was caused by a clogged pipe. I also had some constantly leaky sprinklers that were causing the grass to become soggy and mushrooms were growing. Then I noticed my water bill was several tens

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2020-06-10 Dubbing Adapter

This is an adapter to connect a source such as a smartphone stereo headphone output to the input of an MP3 recorder. The view and diagram is looking at the back of the adapter where the plugs are inserted into the jacks. The switch handles are on the far side. The switch on the right

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2020-05-28 Solid State Shortwave RF Preselector

Comment left 2020 May 29 on YouTube video in the title. This video covers MOSFET, dual gate MOSFET, JFET and BJT tuned preamps (preselectors) for his shortwave crystal radio. “The talk about using 18 volts for the cascode got me thinking about tube designs. When the plates need 100+V, and when the heater to cathode

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2020-03-10 Simple AM Band Antenna Tuning Coil 240 Microhenrys

The standard ferrite antenna loopstick for a 365 pF tuning capacitor has an inductance of about 230 microhenrys. This in combination with the tuning capacitor tunes across the full AM broadcast band. It’s useful to be able to wind your own inductor so it can be used for an antenna coil, a trap to attenuate

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2020-01-23 DIY Variable Capacitor 90 to 3400 pF

The beginning isn’t clear about how it looks. First, scroll to end and look at the photo. https://www.randombio.com/capacitor.html

2020-01-02 Coax Cable and Crimp-On Connectors

FB comment Years ago at work (community college) we had an IBM mainframe and the terminals were connected with coax cables. We also had thin Ethernet cabling. I had the proper connectors and thousand foot boxes of coax, and most importantly the proper stripping and crimping tools. I installed hundreds of coaxes, and I was

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2018-08-29 High Temperature And Nylon Screws

From FB group Hobby Electronics, 2018-09-01 I faced this dilemma before. I’ve repaired power supplies where the transistor failed because it was not held tightly to the heat sink because of a nylon screw that got hot. I used a steel screw and a fiber washer, and heat shrink tubing over the threads to insulate.

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